Not long ago, discrete technologies had discrete purposes. Telephones made calls, office-bound computers accessed databases, and personal digital assistants (PDAs) were simple scheduling devices. The changing, and increasingly mobile, needs of business dictated a new strategy because business communications technologies have converged into a flexible array of services that can be accessed through the enterprise and beyond, by almost any device.
Therefore, mobile computing has become more prevalent. In recent years, there has been an increase in the deployment of notebook personal computers (notebook PCs) and PDAs. This deployment is a result of the increasing need for users to be productive in places other than in the office or behind the desk. Companies are requiring more work to be accomplished with less people. Productivity increases are a key metric for wireless return on investment (ROI). Virtual private networks (VPNs) and wired and wireless modems permit secured access to corporate data outside of the office. In addition, deployments of wireless local area networks (W-LANs) are also increasing in schools and corporate campuses.
Public W-LANs are emerging as a viable alternative to circuit-switched or packet-switched cellular data connections. Moreover, the convergence of voice and data on the LAN is rapidly occurring. Several companies are pushing toward the widespread adoption of Internet Protocol (IP) telephony. Many intra-offices and intra-enterprises are now migrating from traditional circuit-switched solutions to traffic that are transported and switched as packets or cells. Moreover, the standards governing Voice over IP (VoIP), such as H.323, Session Initiation Protocol (SIP), Power over Ethernet (or Power over LAN), for example, are being finalized and established, which further promotes acceptance and adoption of packet-based communications.
Personal computers (PCs), PDAs, and other devices are managing more voice and multimedia communications. More telephones are connected to data networks, or LANs, so that in addition to making calls, they can access directory, messaging, and other database information. Whether in and around the office or campus, at home, or somewhere in between, being connected to these voice, data, and other multimedia resources is critical to meeting the new business demands for productivity and responsiveness.
Session Initiation Protocol-MOBILITY (SIP-M) is application layer mobility. SIP-M depends upon a series of SIP exchanges between a Mobile Node (MN), i.e., a wireless electronic device, and its corresponding hosts (CH) to redirect ongoing connections as one or the other endpoints of those conversations changes its point of attachment to the Internet. In SIP-M, the MN is expected to change its IP address whenever it changes its link-layer point of attachment to the Internet. Both the MN and the CH may understand SIP-M, and the MN and CH may use SIP-M to initiate and establish a communication session. Any application the MN and CH are using may also understand, or not care about, having its IP address change while the MN is changing its location. In order to abide by this requirement, the applications supporting SIP-M may be Universal Data Protocol (UDP)—based, or stateless with a retry scheme, such as Hyper Text Transfer Protocol (HTTP). Alternatively, the applications may have a virtual interface to which the applications bind, where the virtual interface never changes its IP address. The actual physical interface may then deliver packets to the virtual interface after decapsulating the packets or modifying the packets.
Mobile Internet Protocol (Mobile IP) is a lower-level protocol. Mobile IP applications utilize Internet Protocol as a transport mechanism, but depend upon link-layer delivery of datagrams at the first and last hop of the transmission. When a MN or wireless electronic device utilizing Mobile IP changes its point of attachment to the Internet, it does not change its IP address. The Mobile Node instructs a router, referred to as a Home Agent (HA) that its Care-of-Address (COA) has changed. The HA then attracts, via proxy address resolution protocol, or intercepts (by virtue of being the default IP router for the MN when the MN is in the home network), the datagrams, i.e. packets, that are to be delivered to the MN or wireless electronic device. The Home Agent encapsulates the datagrams in a wrapper IP packet with a destination address, addressed to, the Care of Address, and transmits the packets to the Care-of-Address.
The machine resident at the Care-of-Address decapsulates the packet and delivers it to the link layer address of the MN. Generally, outgoing packets from the MN are routed normally using IP-layer mechanisms, but in the case where the default router on a foreign network utilizes the IP source address to determine whether or not to route the packet, i.e., engages in source filtering, the packet may be encapsulated and sent back to the Home Agent for outbound delivery, which is referred to as reverse tunneling.
SIP-M and Mobile IP also directly conflict in the authentication mechanism which allows authorization, authentication, and accounting (AAA). AAA is utilized to allow nodes to use foreign network resources. Mobile IP has a built-in AAA protocol called Mobile IP AAA extensions. SIP-M does not have a built-in AAA protocol. In an embodiment, SIP-M may utilize Protocol for carrying Authentication for Network Access (PANA) for AAA. The AAA methodologies of Mobile IP and SIP-M do not easily combine.
Mobile IP does not require application awareness of mobility. Because of this, Mobile IP is impeded in its ability to handle real-time applications, such as Voice over IP (VoIP) calls. Mobile IP permits a wireless PC, wireless PDA, or other mobile node/wireless electronic device to move from one network link to another without interrupting communications. In an organization with W-LAN, a wireless notebook PC may be physically moved from one building to another, into a new sub-network, without interrupting a file download or video stream, and without requiring users to renew their network/IP address.
On the other hand, SIP-M always utilizes the most direct path for packet delivery, and has a shorter handoff cycle, which makes SIP-M more attractive for real-time application mobility. Unlike the traditional telecommunications model that operates via a central switching element, SIP-M allows the control of services, like telephony, to be moved to the endpoints of a network in SIP-based PDA, notebook PC, Tablet PC clients or SIP-based mobile phones. SIP-M is flexible and extensible, and supports many different types of applications, including video, telephony, messaging or instant messaging, and collaboration.
In an embodiment, SIP-M may be utilized for soft-phone applications, and Mobile-IP may be utilized for legacy applications and those which are not sensitive to delay. Accordingly, a need exists for implementing SIP-M and Mobile IP on the same client device.